The pumps circulate water to regulate temperatures in Unit 2, one of two twin 1,200-megawatt reactors at Limerick. They are not a requirement for a safe shutdown, Exelon said in a release.

The malfunction and shutdown did not rise to any of the levels of emergency classification under the U.S. Nuclear Regulatory Commission (NRC), said Diane Screnci, spokeswoman for the agency.

“Our resident inspectors are there and ensuring that plant workers are appropriately following up and understanding what happened and why it happened and if they have to make any repairs, we’ll be overseeing those,” Screnci said. “There was no impact on the public health and safety, and the plant is stable.”

Exelon lists the total generation capacity at Limerick at 2,317 megawatts, enough power for 2 million homes.

The shutdown comes amid a stretch of warm weather that has air-conditioners buzzing throughout the region.

Exelon did not immediately have a timetable for restoring Unit 2 to service as they were in the process of making repairs, Dana Melia, Exelon’s spokeswoman for Limerick.

“All systems responded as designed and Unit 1 remains at full power,” she said. “Technicians will repair the component and fully test the system before returning Unit 2 to service.”